The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Motors and/or generators, or electric machines, may be constructed using coils and/or permanent magnets. Where permanent magnets are used, the motors and/or generators may be referred to as permanent magnet electric machines. Permanent magnet electric machines are increasing in use in various applications due to the development of magnet materials and power electronics.
Electric machines can include a rotor and a stator where the stator is a stationary portion of the machine and the rotor is a rotating portion of the machine. The machines may include a series of magnets supported on a back iron. The high densities and costs of the materials to form the magnets and the back iron may cause them to be relatively heavy and also relatively expensive. Expense can play a role in the overall cost of a system in which the motor/generator is being used and, as such, reducing expense can offer an economic advantage. The heaviness of the machines may cause them to be less efficient due to higher moments of inertia. For example, a heave rotor may call for higher energy inputs for rotation, thus, reducing the efficiency of the machine. Still further, heavy motors may not be preferred where an overall weight of a system is desired to be relatively low. Accordingly, weight reduction can make motor/generators more efficient and more desirable for purposes of weight reduction of an associated system, for example, in an aerospace application.